Polyesters are polymeric materials made from the esterification of polybasic organic acids with polyhydric acids. Perhaps the most commonly made and used polyester is polyethylene terephthalate (PET), which can be manufactured by reacting terephthalic acid with ethylene glycol.
Polyesters are currently being used in increasing amounts in various applications. For instance, polyesters are commonly used to make many types of beverage and food containers, photographic films, X-ray films, magnetic recording tapes, electrical insulation, surgical aids such as synthetic arteries, fabrics and other textile products.
Because polyesters can be remelted and reformed, ongoing efforts are underway to efficiently recycle as much polyester as possible after use. Before polyester can be recycled, however, it is necessary to separate the post-consumer polyester from contaminants, i.e., materials that may be found mixed with or attached to the polyester. For instance, contaminants can be loose and mixed with the polyester materials, can be attached to the surface of the polyester materials, as with labels attached to the surface of the materials, or can be within the polyester materials, as in the case of embedded or entrained materials.
What is needed in the art are improved methods for removing contaminants from polyester materials, and in particular, from post-consumer polyester materials.